Carbon cell



s. F. LYBARGER CARBON CELL Filed July 15-, 1940 Sept, 39, 1941.

INVENTOR.

{A} ATTORT 'EYS.

W/TNBSJBS.

Patented Sept. 30, 1941 2,257,303 CARBON CELL Samuel F. Lybarger, MountLebanon, Pa., as-

signor to E. A. Myers & Sons, Mount Lebanon, Pa., a partnershipconsisting of Edward A. Myers, Edwin J. Myers, Alfred E. Pelz, and

Samuel F. Lybarger Application July 13, 1940, Serial No. 345,435

7 Claims.

This invention relates to carbon cells by which an electric current isvaried in a microphone, amplifier or the like, and especially to thoseused with hearing aids for the hard of hearing.

durable and dependable, and which is relatively simple and inexpensivein construction.

In accordance with this invention two electrode members are disposedadjacent each other with The simplest type of carbon cell or microphonea space between their opposed surfaces in which cell consists of twoflat conducting plates With a a quantity of carbon granules or the likeare space between them filled loosely with granular contained in a loosemass. The space between carbon. When operated with the conducting theouter edges of the electrodes is sealed to hold plates in a verticalposition this cell has a very the granules in place, but the sealingmeans is high emciency, probably higher than most other 10 sufficientlyyielding to permit one of the electrodes types, because the vibration ofthe movable plate to vibrate relative to the other one in order to orelectrode is in a direction at right angles to the vary the pressure onthe granules and thereby conducting surfaces, whereby the carbongranuvary the electric current flowing through the lar mass is given themaximum compression for cell. The vibratable electrode may be actuated agiven relative movement of the two plates by the armature of anamplifying unit, or ditoward each other. The principal disadvantagerectly by sound waves as in a microphone. For of such a cell is that theefficiency depends upon efficient operation the electrodes have opposedits position, and. if the plates are horizontal the surfaces that aredisposed at a relatively great carbon falls entirely away from one plateso that angle to the axis of the cell, as much as 90 if the cell iscompletely open circuited. A number desired, although a somewhat smallerangle is of ways have been proposed to overcome the preferred. Toprevent the carbon granules from difiiculty, such as by the use ofconcentric conical falling away from the upper electrode surface orhemispherical electrodes, but none has been when the cell is lying flatwith either side up, the entirely successful. central and marginalportions of the electrodes In the present invention a novel and morehave their opposed surfaces disposed in the mansatisfactory arrangementof the electrodes is ner just recited and they are connected by theemployed than ever used heretofore. Fundaopposed surfaces of theintermediate portions of mentally, this cell really consists of twosepathe electrode members which are disposed at a rate cells,oneconsisting of two circular elecsmaller angle to the axis of the cell.The space trodes suitably spaced apart and the other conbetween theseintermediate portions is therefore sisting of two annular electrodes ofgreater dimore nearly vertical when the cell is lying flat, ameterlikewise spaced apart. The two cells are and forms a conduit or channelfor the carbon spaced axially from each other and are congranules thatpermits them to flow from the nected by an annular passageway to permitthe upper part of the cell to the lower part. The free flow of carbonfrom one cell to another. granules in this so-called conduit also form aWith this arrangement excellent operation is sehead so that the granulesbetween the more cured with the common axis of the cells horinearlyhorizontal lower surfaces of the electrodes zontal. In this positionpractically all of the make good contact with the electrode surfaces.smaller circular cell is active, as well as a por- The intermediateportions of the electrode memtion of the larger annular cell. When theaxis bers are preferably so arranged that but little of the cells isvertical with the smaller cell uppercurrent flows between them. most,the carbon granules, which only partially The invention is illustratedin the accompanyfill the unit fall away from the upper electrode ingdrawing in which Fig. 1 is a plan view of a of the upper cell, .but thelower cell is totally hearing aid amplifier or intensifier with the topactive. With the larger cell uppermost the of its cover cut away andembodying my invenopposite is true. The carbon in the channel or tion;Fig. 2 is a vertical longitudinal section passageway between the twocells provides in each through the amplifier; Fig. 3 is a verticaltranscase a head of pressure to insure that the converse section takenon the line IIIIII of Fig. 2; tact between the granules and electrodesis ade- Fig. 4 is a transverse section of the carbon cell quate, but notso large as to pack the carbon. An alone disposed with its vibratoryelectrode at the appreciable amount of microphonic action may bottom;Fig. 5 is a view similar to Fig. 4 with the also occur in this channel.vibratory electrode at the top; and Fig. 6 is a It is among the objectsof this invention to vertical section through a modification of thisprovide a carbon cell of this character which invention.

Referring to the first three figures of the draw functions efficientlyin any position, which is ing, on the upper surface of a base plate I,preferably made of a suitable insulating composition, there is mounted ablock 2 of cold rolled steel or similar material that functions as apart of the magnetic circuit of the electromagnet of the amplifier, andalso as a support for various other amplifier parts. This block isprovided at one end with an L-shaped projection 3 spaced from the baseand secured to the lower end of an upwardly extending armature 4.Fastened to the opposite end of the block is an upwardly extendingpermanent bar magnet 6 the upper portion of which carries a pole piece7. The pole piece overlaps the outer surface of the magnet with itslower end fastened thereto by means of screws 8, and extends inwardlyacross the top of the magnet, then downwardly a short distance and thenlaterally away from the magnet. The latter portion of the pole piececarries a coil 9 and is placed a short distance from armature 4 to forman air gap. The spacing of the gap may be varied by a set screw Hthreaded in the overlapping portion of the pole piece and bearingagainst the magnet. The construction described thus far is substantiallythe same as that disclosed in my Patent No. 2,145,603.

At the side of the armature opposite to the magnetic coil a carbon cell2| is mounted. The housing for this cell is a ring 22 having an innerradial flange 23 at its inner edge. The housing is rigidly supported inposition by means of horizontal rods 24 connected to flange 23 and across bar 26 the central portion of which is fastened to the inner faceof magnet 6. The two sides of the cell between which the usual carbongranules 2'! are disposed are formed by two circular diaphragm-likeelectrodes 28 and 29. The inner electrode 28 is rigidly connected to theupper end of armature 4, and to permit it to be vibrated thereby itsedge is held rather loosely within ring 22 between a pair of softgaskets 3|. The outer electrode 29 is rigidly mounted in the ring thedesired distance from the inner electrode between a hard insulatingspacing washer 32 engaging a radial shoulder 33 in the ring, and

a thin insulating washer 34 clamped against the outer electrode by aretaining ring 36 screwed in the outer end of the housing ring.

As shown in Fig. 2, the electric circuit through this carbon cell ismade through a jack plug 3'! depending from base I of the amplifier,block 2, armature 3, the inner electrode, the carbon granules, the outerelectrode, and through a wire 38 connected to the latter and to aterminal 39 that is engaged by a spring conductor 4! connected to a plugsocket 42 mounted in the cover 43 of the instrument.

It is a feature of this invention that this carbon cell operatessatisfactorily regardless of the position in which it may be held.Accordingly, both electrodes are concave or generally cupshape with theouter electrode projecting or nested into the inner-one concentricallytherewith. The central and marginal portions of the two electrodes aredisposed at relatively great angles to their axis, as shown in Fig. 2,so that the cell will function eificiently. These two portions of theelectrodes are connected by their intermediate portions which aredisposed at a materially smaller angle to the axis of the cell so thatwhen the cell is lying fiat with either electrode uppermost (Figs. 4 andsome of the carbon granules in the upper portion of the cell will freelysettle down through the intermediate space and by their weight hold thegranules in the lower portion of the cell against both elec trodes inorder to provide good contact with them. Although the central andmarginal portions of the electrodes might be disposed at 90 to theiraxis, it is found that the granules flow from one part of the cell toanother more freely if the angle is about 60. In such a case theelectrodes of the two most active portions of the cell are not far frombeing flat, resulting in high efficiency because of the directcompression of the carbon granules between them. The conical form,however, permits easy movement of the granules from one portion of thecell to another, and the contact of the carbon against 'ie electrodesadjacent the connecting channel is greatly improved. The connectingchannel should make a relatively small angle with the axis of the cellso that a relatively long channel is formed without unduly increasingthe diameter of the cell. Such a channel gives a better head of carbonwhen the axis is vertical and results in more stable operation.

As the intermediate portions of the electrodes are disposed at a smallerangle to the axis of the cell than the central and marginal portions, itfollows that vibrations of the inner electrode do not act upon thecarbon granules in the interm diate space in as pronounced a manner ason the granules in the other parts of the cell. Therefore, it isdesirable that only a relatively small percentage of the total electriccurrent should flow across that intermediate space, because it will notbe used as effectively as elsewhere in the cell. Accordingly, theintermediate portions of the electrodes may be spaced farther apart thanthe central and marginal portions, thereby increasing the resistance toflow of current between them and confining as greater portion of currentflow to the central and marginal portions of the cell.

In the modification shown in Fig. 6 the outer electrode member, insteadof being a diaphragm, is a multiple part member formed from an outerdisc 5i screwed into the housing ring 22 against spacing washer 32, aconical inner element 52 having an integral pin 53 extending outwardlythrough the center of the disc, and a frustoconical intermediate member54 encircling the pin. These three elements are rigidly connectedtogether by a nut 56 threaded on the end of the pin. Intermediate member54 is a non-conductor of electricity so that current will not flow fromit across the intermediate portion of the space between the twoelectrodes.

Another important feature of this invention is that the shape of thevibratory electrode is such that very high mechanical strength exists,permitting the use of extremely thin brass or aluminum for thiselectrode. The low mass of this moving part contributes to good highfrequency response in the device in which it is used. Brass only twoone-thousandths of an inch thick, gold plated to provide a good contactsurface, has been found very strong and light.

According to the provisions of the Patent Statutes, I have explained theprinciple and construction of my invention, and have illustrated anddescribed what I now consider to be its best embodiment. However, Idesire to have it understood that, within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallyillustrated and described.

I claim:

1. A carbon cell comprising a cupped electrode member, a secondelectrode member projecting into the cupped member and spaced therefrom,said members having central portions and marginal portions connected byintermediate portions, and carbon granules occupying the space betweensaid electrode members and adapted to engage said portions thereof, theopposed surfaces of said central and marginal portions of said membersbeing conductors of electricity and being disposed at a greater angle tothe axis of the members than the angle at which the 010- posed surfacesof said intermediate portions of said members are disposed relative tosaid axis.

2. A carbon cell comprising a cupped electrode member, a secondelectrode member projecting into the cupped member and spaced therefrom,said members being of general conical shape and having central portionsand marginal portions connected by intermediate portions, and carbongranules occupying the space between said electrode members and adaptedto engage said portions thereof, the opposed surfaces of said centraland marginal portions of said members being conductors of electricityand being disposed at a greater angle to the axis of the members thanthe angle at which the opposed surfaces of said intermediate portions ofsaid members are disposed relative to said axis.

3. A carbon cell comprising a cupped electrode member, a secondelectrode member projecting into the cupped member and spaced therefrom,said members having central portions and marginal portions connected byintermediate portions, and carbon granules occupying the space betweensaid electrode members and adapted to engage said portions thereof, theopposed surfaces of said central and marginal portions of said membersbeing conductors of electricity and being disposed at a greater angle tothe axis of the members than the angle at which the opposed surfaces ofsaid intermediate portions of said members are disposed relative to saidaxis, said opposed surfaces of the intermediate portions being spacedfarther apart than said central and marginal portions.

i. A carbon cell comprising a pair of cupped electrodes nested in spacedrelation and having central portions and marginal portions connected byintermediate portions, and carbon granules occupying the space betweensaid electrods and adapted to engage said portions thereof, the innersurfaces of said central and marginal portions of the electrodes beingconductors of electricity and being disposed at an angle of more than 45degrees to the axis of the electrodes, and the inner surfaces of saidintermediate portions of the electrodes being disposed at a smallerangle to said axis.

5. A carbon cell comprising a pair of cupped electrodes nested in spacedrelation and having central portions and marginal portions connected byintermediate portions, and carbon granules occupying the space betweensaid electrodes and adapted to engage said portions thereof, the innersurfaces of said central and marginal portions of the electrodes beingconductors of electricity and being disposed at an angle of more than 45degrees to the axis of the electrodes, and the inner surfaces of saidintermediate portions of the electrodes being disposed at a smallerangle to said axis and being spaced farther apart than said central andmarginal portions.

6. A carbon cell comprising a cupped electrode member, a secondelectrode member projecting into the cupped member and spaced therefrom,said members having central portions and marginal portions connected byintermediate portions, and carbon granules occupying the space betweensaid electrode members and adapted to engage said portions thereof, theopposed surfaces of said central and marginal portions of said membersbeing conductors of electricity and being disposed at a greater angle tothe axis of the members than the angle at which the opposed surfaces ofsaid intermediate portions of said members are disposed relative to saidaxis, said intermediate surfaces of at least one of said electrodemembers being a nonconduotor of electricity.

'7. A carbon cell comprising a cupped electrode member, a secondelectrode member projecting into the cupped member and spaced therefrom,said members having central portions and marginal portions connected byintermediate portions, and carbon granules occupying the space betweensaid electrode members and adapted to engage said portions thereof, theopposed surfaces of said central and marginal portions of said membersbeing conductors of electricity and being disposed at a greater angle tothe axis of the members than the angle at which the opposed surfaces ofsaid intermediate portions of said members are disposed relative to saidaxis, said intermediate portion of said second electrode member being afrusto-conical insulator.

SAMUEL F. LYBARGER.

